In an age of deficits, beware of politicians offering something for nothing

What links school meals, marriage, and green taxes? They are all areas where politicians want to offer you something for nothing.

The freebies on school meals and marriage are already agreed, dished out at the Lib Dem and Tory conferences. Each is worth around £600 million. Of that £1.2 billion, how much is deadweight cost or just plain waste, money going to people who don't need it? HM Treasury won't say, but my back-of-an-envelope guess is more than half, a guess partly informed by David Cameron's candid admission that his married couple's tax break "is not about the money". That's quite a thing to say about a policy that will entail one o the following: raising another 600 million quid in tax elsewhere; cutting another 600 million quid in spending somewhere else; or borrowing another 600 million quid. We may, just, find out at the Autumn Statement in December.

As for green taxes, the Government hasn't given you anything – yet. Some Conservatives are keen though. You can see why: people are angry about energy bills, and cutting the environmental levies on them would mean those bills rise a little less quickly than they do right now. Still, there's another thing about green taxes that's worth remembering: they raise revenue for HMG. So cutting them means less revenue. And that means one of three things: higher tax elsewhere; more cuts in spending elsewhere; or higher borrowing.

You'll have noticed that I've made the same, not very subtle point, a couple of times. I've done it because some politicians seem to have forgotten an awkward fact: there is no such thing as free money. Everything Governments do has to be paid for, one way or another. Right now, when the Government is spending £120 billion a year more than it raises in tax, that means borrowing money, money that will have to be paid back eventually. And guess who's going to do the paying?

On current plans, deficits – and the borrowing they entail – are going to go on beyond the next general election until almost the end of the decade. Yet politicians, some Conservatives included, are acting as if an age is plenty is just around the corner.

Yes, the economy is starting to look up, but only after years that have done stunning damage to the public finances.

Will growth bounce back to above-trend levels within the next two years? Will tax revenues come in well above forecast, giving HM Treasury bags of spare cash to play with? Some serious economists are publicly predicting the former. Some serious Cabinet ministers are privately speculating on the latter. But neither is certain, and voters should apply a healthy scepticism to politicians' promises of jam today. And George Osborne should be commended for offering a less popular, but more realistic message, on the deficit and the difficulties of giveaways.